A non-return flow valve for valving the flow of molten plastic in a plastic injection molding machine, said machine having a barrel and a reciprocating feed screw mounted in a bore in said barrel, said valve comprising:
- (a) valve body means, said valve body means including,
- (i) means for connecting said body means to said feed screw,
- (ii) a cylindrical body portion,
- (iii) a shoulder portion extending outward radially from said cylindrical body portion, said shoulder portion spaced axially from said connecting means, said cylindrical body portion disposed intermediate said shoulder portion and said connecting means;
- (b) first valve seat means slidably received over said cylindrical body portion, said first valve seat means including means defining:
- (i) a first valve seating surface,
- (ii) a plurality of flow passageway means formed in said first valve seat means, said flow passageway means in fluid communication with said first valve seating surface at the inlet end thereof, and,
- (iii) a generally transverse surface portion in abutment with said shoulder portion;
- (c) a second valve seat means slidably received over said cylindrical portion, said second valve seat means including means defining,
- (i) a transverse surface portion engageable with said feed screw,
- (ii) a second annular valve seating surface disposed axially opposite said transverse surface;
- (d) a tubular spacer slidably received over said cylindrical portion, said spacer disposed intermediate said first and second valve seat means for establishing a predetermined spacing between said first and second valve seating surfaces;
- (e) an annular valve member received over said body means, said valve member having,
- (i) an outer cylindrical surface portion adapted for closely fitting, sliding relationship with said barrel bore,
- (ii) a first annular valve surface formed on one end face thereof,
- (iii) a second annular valve surface formed on the other end face thereof, said second valve surface disposed opposite said first valve surface,
- (iv) said first and second valve surfaces longitudinally spaced an amount less than said predetermined spacing between said first and second valve seating surfaces,
- (v) an inner cylindrical surface portion having an internal diameter greater than the outer diameter of said tubular spacer for defining an annular fluid passageway therebetween;
- (f) anti-rotation means for preventing rotation of said first valve seat means relative to said valve body means, said anti-rotation means including,
- (i) a radially extending pin having a first portion thereof mounted in a bore in said cylindrical body portion and a second portion thereof extending outwardly therefrom,
- (ii) said first annular valve seat means has a cylindrical bore formed therethrough and in closely fitting relationship to said cylindrical body portion, and an axially extending notch formed into said cylindrical surface portion adjacent said transverse surface portion, said second portion of said pin extending into said notch;
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- (g) said valve member movable between an open position in which said first valve surface is in abutment with said first valve seating surface in which molten plastic flows from said feed screw between said second valve surface and said second annular valve seating surface, through said annular passageway, and exhausting through said flow passageways in said first valve seat means exteriorly of said one-way flow valve, said valve member movable to a closed position in which said second valve surface is in sealing abutment with said second valve seating surface such that said molten plastic is prevented from flowing toward said feed screw.